When using a winch to raise a payload, a winch cable is attached to a motor-driven drum at one end and the payload at the other. The motor is driven to rotate the drum in order to gather up the winch cable on the outer circumference of the drum. A clutch is provided to transmit torque from the motor to the drum. The clutch allows the setting of a maximum torque above which the clutch will slip. When the clutch slips, this effectively disconnects the drum from the motor. This disconnection function prevents an overload experienced at the payload from damaging the winch or a structure to which it is attached (e.g. an airframe). The maximum torque setting of the clutch relies on the degree of bias acting on the plates of the clutch and the coefficient of friction between the plates, as understood by one skilled in the art. Unfortunately, it has been found that current clutches can exhibit unacceptable variation in the friction properties between clutch plates during use, which may prevent slipping at a desired maximum transmitted torque setting or allow premature slipping, before the maximum transmitted torque setting is reached.
A means for setting the maximum transmitted torque is therefore needed to improve on current winch clutch design and increase reliability, safety and stability.